Hydropneumatic chuck actuating device

ABSTRACT

A hydropneumatic chuck-actuating device comprises a double walled tubular body with a central bore adapted to receive a chuck and an annular chamber defined between the walls of the body. The annular chamber is divided by a fixed annular piece into parts of different transverse cross-sectional area. Primary and secondary annular pistons are slidably mounted in the annular chamber about a hydraulic fluid, in a manner to multiply a pneumatic force applied on the primary piston into a greater force on the secondary piston which actuates closing of the chuck. Opening of the chuck is provided by simultaneously pneumatically acting on the two pistons.

United States Patent 11 1 1111 3,835,649 Le Testu Sept. 17, 1974 HYDROPNEUMATIC CHUCK ACTUATING 3.087.736 4/1963 Lukas 279/4 DEVICE 3.389.557 6/1968 Backc ct al...... 60/593 3426530 2/1969 Gcorgclin 60/583 [76] Inventor: Claude Le Testu, 20 rue des Buttes,

74300 Cluse5- France Primary Examiner-EdgarW. Gcoghegan 22 Filed: May 29 1973 Assistant ExaminerA. M. Zupcic Attorney, Agent, or FirmRobert E. Burns; PP NOJ 3641245 Emmanuel J. Lobato; Bruce L. Adams [30] Foreign Application Priority Data [57] ABSTRACT May 29, 1972 France 72.19407 A hydropneumatic chuck'acwating device Comprises a double walled tubular body with a central bore 52 U.S. c1 60/560, 60/583, 60/593, 1 adapted to receive 21 Chuck and an annular Chamber 179/4 defined between the. walls of the body. The annular 51 Int. Cl. FlSb 7/00 Chamber is divided by a fixed annular Piece Parts [58] Field of Search 60/547 560, 565 583 of different transverse cross-sectional area. Primary 60/593; 179/4 and secondary annular pistons are slidably mounted in the annular chamber about a hydraulic fluid, in a man- [56] References Cited ner to multiplyga pneumatic force applied on the pri- UNITED STATES PATENTS mary piston into a greater force on the secondary piston which actuates closing of the chuck. Opening of 6 the chuck is provided by simultaneously pneumatically 2,948,542 8 1960 Leifcr 279/5 actmg on the two 3,072,416 1/1963 -1 Claim, 6 Drawing Figures Lcifcr 279/4 PAIENIEU SEPI 71914 SHEET 2 OF 3 PAIENTED SEP I 71814 SHEU 3 BF 3 HYDROPNEUMATIC CHUCK ACTUATING DEVICE The invention relates to hydropneumatic or pneumohydraulic devices for actuating chucks, principally for use in machine tools for gripping workpieces.

According to the invention, a hydropneumatic chuck-actuating device comprises a primary piston which is pneumatically actuated for movement in either direction, said primary piston acting hydraulically on a secondary piston adapted to actuate a chuck, the ratio of the cross-sectional areas of these pistons being such that the pistons form a force-multiplying device, characterised by the fact that it comprises an annular chamber surrounding the chuck, said annular chamber being divided by a fixed intermediate piece into two communicating cylindrical parts of different transverse cross-sectional areas, the primary and secondary pistons being annular and being slidably received in respective ones of the parts of said annular chamber with a hydraulic fluid disposed between a front face of the primary piston and a rear face of the secondary piston, a primary air chamber behind the primary piston, and two secondary air chambers, one in front of the primary piston and the other in front of the secondary piston.

The accompanying drawings show, by way of example, two embodiments of the invention. In the drawings: 30

FIG. 1 is an axial cross-section of a first embodiment of the invention, taken along line [-1 of FIG. 2;

FIG. 2 is a plan view of the first embodiment;

FIG. 3 is an axial cross-section of a second embodiment of the invention, taken along line IIIIII of FIG. IV:

FIG. 4 is a schematic plan view of the second embodiment;

FIG. 5 is a partial cross-section taken along line V-V of FIG. 4; and

FIG. 6 schematically shows a simplified arrangement for the pneumatic control of either of the embodiments.

With reference to FIGS. 1 and 2, the first embodiment of device comprises a tubular cylindrical body I 45 having a central cylindrical bore 27, Oin the lower part of body 1 bore 28 6f slightly greater uiameter than bore 27 is machined. In the bore 27 is fitted a cylindrical sleeve 29 having an outer flange 3 which is tightly fitted in bore 28 and fixed by a circular clip or split ring 6 adapted to take up play. Sleeve 29, which defines with bore 27 of body 1 an annular cylindrical chamber, receives an F-type chuck 4 which is centered by the sleeve 29. An optional cylindrical stop member 5 can be force fitted in the lower end of sleeve 29, and includes an adjustable central projection terminating at 50 which cooperates with chuck 4 for the purpose of adjusting the axial position of a piece gripped by the chuck 4.

In the lower part of said annular chamber is lodged a primary piston 7 provided with two joints 8 and 9 and a third, lip-type, joint 10 ensuring a fluid-tight joint between the wall of the annular chamber formed by the outer face of sleeve 29 and a cylindrical inner wall of a fixed annular piece 1 1 serving to separate the said annular chamber into two parts. Piece 11 is held in place by means of a circular clip or split ring 12 and is pro- 5 joint 30. The purpose of joints 8, 9, 13, 13' and 30 is to provide an air-tight joint for compressed air supplied by means which will be described further on, while the lip-edged type joints l0, l5 and 16 serve to provide liquid-tightness for an oil located in a hydraulic chamber 3l/32 defined between primary piston 7, piece 11 and secondary piston 14.

Compressed air to ensure a tightening of chuck 4 is supplied by an inlet 17 provided with a quick-fitting adaptor, and compressed air to ensure a loosening of chuck 4 is supplied by a similar inlet 22. Inlet I7 is connected by a channel 33 to a primary air chamber 19 situated behind (ie at the lower end of) the primary piston 7, and inlet 22 is connected by a channel 23 to two secondary air chambers one of which, 20, is located above primary piston 7 and the other of which, 21, is located above the secondary piston 14.

The flange 3 includes two bores 34, 35, disposed generally parallel to the axis of the device, communicating respectively by a channel 36 with the primary air chamber 19, and by a channel 24 with the two secondary air chambers 20 and 21. These bores 34, 35 are either closed by stoppers, not shown, in which case inlets 17 and 22 are employed, or the inlets 17 and 22 are closed by stoppers and bores 34, 35 are used in their place.

To assemble the device, the secondary piston 14, the intermediate fixed part 11, the primary piston 7 and sleeve 29 with its flange 3 are successively placed, with their respective joints, into the body 1. The oil is introduced into chamber 31/32 by a lateral conduit 37 in body 1 which is then closed by a screwed plug 38.

The upper end of secondary piston 14 has a cylindrical outer surface 14b and an inner trunco-conical surface l4a cooperating with trunco-conical outer surfaces of the jaws of chuck 4. Surface 14b is slidably received and guided in a narrowed cylindrical end of body 1. Chuck 4 is axially held in its housing in body 1 by means of a screwed ring 25.

Body 1 is also provided in the lower part of its outer surface with an annular dove-tail groove 39 enabling the device to .be precisely and reliably fitted onto a plate of a lathe by means of three self-clamping pieces 2 fixed by means of screws 41.

The described device operates as follows:

To close the jaws of chuck 4, compressed air is delivered, via inlet 17 or bore 34, to the primary air chamber 19 and tends to push primary piston 7 upwards. The upper end of lesser cross-sectional area of this piston 7 applies a pressure to the oil in chamber 31/32. This pressure acts on the secondary piston 14 over a relatively greater area, so that the upward force on piston 14 is a multiple of the force applied by piston 7, and this force is applied, by the trunco-conical surface 14a of secondary piston 14, to the jaws of chuck 4 which tend to close. To loosen the jaws of chuck 4, compressed air is delivered, via inlet 22 or bore 35. to the secondary air chambers 20 and 21; the pressure of this air acts on equal surface areas of the primary and secondary pistons which produces a downward movement of the two pistons to their lower positions, as shown, and a corresponding freeing of the chuck 4.

The embodiment shown in FIGS. 3 to 5 is a variation of the first embodiment and similar parts are indicated by the same reference numerals with a prime designa tion. The construction and operation of this variation are substantially the same as for the first embodiment, and will therefore not be described in detail, but differ in the following respects. The uniform bore 27 of body 1' is replaced by two cylindrical bores 42 and 43 connected by a trunco-conical face 44, the lower bore 43 being of greater diameter than the upper bore 44. This facilitates the successive mounting of the secondary piston 14, the intermediary fixed part 11 and the primary piston 7' in the body 1.

The device is also provided with a known type of oil compensating device including an adjustable piston 45 (FIG. provided with a joint and being movable by means of a screw 46, shown in a broken-line screwed into an internally threaded stopper 47. Piston 45 moves in a chamber 60 communicating by a channel 61 with a supply groove 62 (FIG. 3) leading into an oil chamber The purpose of this oil compensator is to enable the position of the secondary piston 14 to be adjusted as a function of the diameter of the standard type of chuck 4 used which is liable to vary slightlyfrom one chuck to another.

The supply groove 62 has bevelled, trunco-conical edges to facilitate the passage of the joint 49 during the insertion of secondary piston 14. Another feature is the absence of lip-edged type joints. Joint is replaced by a joint 48 housed in an annular groove of piece 1 l, and joint is replaced by a joint 49 housed in an annular groove in the outer face of secondary piston 14'. The overall outer shape of body 1 is that of a rectangular parallelepiped, so that the device can be fixed upright or on one of its side faces, two pairs of dove-tail grooves 50, 51 and 52, 53 being provided for this purpose. The device also includes a fixed, screwably mounted stop 5'.

FIG. 6 schematically shows either of the described embodiments of device fixed by its body 1 onto a plate 40 of a lathe including a schematically indicated rotatably driven shaft or spindle 53. By means of a known type of rotary twin channel connector 54, longitudinal conduits 55, 56 of shaft 53 are connected to a four-way pneumatic distributor 26 controlled by two end-of-path stops 57 and 58 which are mechanically actuated by a member 59 which moves to-and fro, as indicated by double-headed arrow F, in synchronization with reciprocation of a cutting tool of the lathe. Conduits 55, 56 are connected to bores 34, 35 to control the opening and closing of the the chuck in synchronization with operation of the lathe, the inlets l7 and 22 being blocked by appropriate means.

The control arrangement shown in FIG. 6 is in fact greatly simplified and in practice a rapid differential discharge valve and a no-return valve would be added. These control systems are, of course, well known to those skilled in the art.

It can be seen that the described embodiments of the invention provide a particularly compact and robust unit which enables a very precise control of the chuck and which can be easily fitted on most machine tools. Also, these devices, although having a relatively small volume, enable a very great gripping power to be obtained. The provision of communicating secondary air chambers for acting on both the primary and secondary pistons has the advantage that opening of a chuck held in the device is reliable. Another advantageous feature is that the principal metal components of the described embodiments can all be relatively easily manufactured by turning operations, and can be assembled together without a need for screw threads. The devices can be used with commercially available F and W chucks. Of course, the chuck jaws, instead of being pushed to close them, could as is known be actuated by a pulling action.

What is claimed is:

1. A hydropneumatic chuck-activating device comprising a double-walled cylindrical body having a central bore for receiving a chuck therein and a closed annular chamber defined between said walls of said body, a fixed cylindrical piece disposed between said walls of said body dividing said annular chamber into a central cylindrical annular part having a transverse crosssectional area less than said annular chamber, and first and second cylindrical annular parts of greater transverse crosssectional area than said central part, said first and second parts of said annular chamber being disposed on opposite sides of said cylindrical piece, a primary annular piston having a sleeve extending into said central part of said annular chamber and slidably mounted in said first part of said annular chamber, a secondary piston slidably mounted in said second part of said annular chamber, a hydraulic fluid chamber defined in said second part and in said central part of said annular chamber between said sleeve of said primary piston and said secondary piston, a first air chamber defined in said first part of said annular chamber and limited by a face of said primary piston opposite said cylindrical piece, communicating second air chambers one of which is defined in said second part of said annular chamber and limited by a face of said secondary piston opposite said cylindrical piece, and the other of which is defined in said first part of said annular chamber between said cylindrical piece and said primary piston, means on said secondary piston for closing said chuck disposed in said central bore, means for delivering compressed air to said first air chamber for actuating said first piston to actuate said second piston to close said chuck, means for delivering compressed air to said communicating second air chambers to actuate said pistons to release said chuck from said closed condition, and means holding said chuck in said central bore. l l 

1. A hydropneumatic chuck-activating device comprising a doublewalled cylindrical body having a Central bore for receiving a chuck therein and a closed annular chamber defined between said walls of said body, a fixed cylindrical piece disposed between said walls of said body dividing said annular chamber into a central cylindrical annular part having a transverse crosssectional area less than said annular chamber, and first and second cylindrical annular parts of greater transverse crosssectional area than said central part, said first and second parts of said annular chamber being disposed on opposite sides of said cylindrical piece, a primary annular piston having a sleeve extending into said central part of said annular chamber and slidably mounted in said first part of said annular chamber, a secondary piston slidably mounted in said second part of said annular chamber, a hydraulic fluid chamber defined in said second part and in said central part of said annular chamber between said sleeve of said primary piston and said secondary piston, a first air chamber defined in said first part of said annular chamber and limited by a face of said primary piston opposite said cylindrical piece, communicating second air chambers one of which is defined in said second part of said annular chamber and limited by a face of said secondary piston opposite said cylindrical piece, and the other of which is defined in said first part of said annular chamber between said cylindrical piece and said primary piston, means on said secondary piston for closing said chuck disposed in said central bore, means for delivering compressed air to said first air chamber for actuating said first piston to actuate said second piston to close said chuck, means for delivering compressed air to said communicating second air chambers to actuate said pistons to release said chuck from said closed condition, and means holding said chuck in said central bore. 